http://codsm.org/forums/showthread.php?t=3965


Informative thread where a chemist tests the E85 “Goo” and explains what he thinks it is. It's 7 pages or so an gets a little long winded...

In a nut shell it’s in the fuel, not the lines tanks etc like so many believe. It’s basically an additive that’s gas station specific and or old additives ”gum” that has accumulated in old tanks that they filled with ethanol. This also explains why some areas have “goo” while others do not.

It will not clog fuel pumps, injectors, filters etc as it is soluble in its liquid E85 state. As the ethanol/gas mixture exits the injector the additive crashes out of the mixture and builds up in the intake/injector tips etc. After a hot engine is shut down and fuel slowly dribbles out of the injectors due to the system being pressurized the gas and ethanol evaporate and the “goo” crashes out of the mixture and builds up on injector tips. This may also explain why I haven’t seen much in the way of goo on my current car. U run no check valve in the fuel system. When I shut the car down pressure instantly drops to zero and I get to leakage past the inj tips. I also believe injector design/atomization and leakage all play a big roll.

The chemist in the thread suggests a 15% addition of race fuel and or toluene/xylene should be enough to break down the sticky gum formation and “clean” the goo away. So about 2 gallons of race fuel per 12 gallon tank should solve the problem. He suggested 100 octane unleaded race fuel. Seems like this would be a pretty cheap and easy solution to me. Higher percentages will clean the goo buildup more quickly, and maintaining 15% mixture should eliminate the buildup.

Adding 15% of any fuel that readily dissolves this “Goo” compound will work as well, (pump premium grade 91-93 octane) but it will also drop the octane of the “E85” significantly.

Heres a few pics of the goo on my injectors. I've dealt with this stuff for years.


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Thanks for the link. My e85 buddies around here all had the goo. Most of them switched to buying denatured ethanol in 55 gallon drums.